Energy scavenging research shows a growing interest these last years. This paper aims to demonstrate the ability of micromachined vibrating structures to store mechanical energy and then to convert it into electrical energy through a piezoelectric plate. Such a micro power generator may be used as a mechanical to electrical energy transformer. The energy conversion consists in a mechanical shock enabling to convert low vibrating energy levels at very low frequencies (typically below 10 Hz for human being excitation source) to mechanical energy to the vibrating structure for which resonant frequencies are ranging from 10 kHz to 1 MHz. Moreover this basic low frequencies to high frequencies spectrum conversion enables to avoid frequency tuning designing that is required for adapting the frequency spectrum of the excitation source.

Mass-sensitive electro-acoustic devices such as surface acoustic wave (SAW) micro-balances, capable to operate with aqueous media are particularly favorable for the development of biosensors. Their dimensions and physical properties offer a large potential in biological fluid investigations, especially for measuring physical phenomenon (mass deposition, adsorption, pressure…). In this work, we propose a specific grating configuration to lower the influence of viscosity of fluids which reduces the signal dynamics of the surface wave transducers. A dedicated liquid cell also has been developed to isolate the electro-active part of the device. The fabrication of the cell is achieved using theSU-8™ photo-resist, allowing for manufacturing thick structures preventing any contact between the tested liquids and the transducers. Furthermore, the sensing area has been optimized to optimize the sensor gravimetric sensitivity. The operation of the sensor is illustrated by detecting bovine serum albumin (BSA) adsorption in the sensing area.

International audienceThe performances of quartz tuning forks (QTF) used in infrared spectroscopy for pollutant detection are investigated. The transduction between light and QTF vibration is elucidated thanks to QTF encapsulation under vacuum. From the sensitivity enhancement which is obtained we conclude that their interaction is photo-thermoelastic rather than photo-thermoacoustic. A mapping of the local sensitivity of the QTF is obtained by scanning its faces with the excitation probe beam. The comparison between the signal mapping and the theoretical strain mapping indicates that the most efficient areas of the QTF correspond to the areas where the strain or stress are the highest